Manufacturing and uses of backing foils – some technical experiments

Hello, I am Christiane Stempel, goldsmith, conservator and responsible for the technological examination of Early Medieval garnet objects that have been brought to the Römisch-Germanisches Zentralmuseum in Mainz for scientific analyses within the project “Weltweites Zellwerk”.

During my work, I made some observations that raised questions regarding the manufacturing and the use of the patterned foils behind the garnets.

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Fig. 1: Schematic figure of an Early Medieval garnet cloisonné (photo: RGZM/Ober)

Transparent stones were often underlaid with gold foils to reflect the light through the stone. This is particularly important when the stone is backed up with cement. In the Early Medieval period textured backing foils were used on a large scale. The three-dimensional pattern increased the reflective effect. I examined a great number of objects from different find-spots in Sweden, Anglo-Saxon England and the Rhineland and I found all the varieties of pattern commonly known from the literature such as standard waffle, boxed waffle (Varying in the number of enclosed squares [9 to 25]), ring-and-dot, lozenge, boxed lozenge and rectangle (stack bond). They only differ in fineness (number of lines/mm), depth of texture and contour sharpness.

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Fig. 2 a-f: Foil pattern (RGZM/Stempel)

 

Unfortunately, the project nears its end and I would like to use the remaining time to carry out some technical experiments:

Producing the pattern

There are indications (see figures 3-7) that at least a number of foils weren’t manufactured with dies. It looks as if lines were traced immediately on to the foils to form the grid pattern.

Fig. 3: Buckle, Ailenberg, Württembergisches Landesmuseum Stuttgart A.V. III333 (photo: RGZM/Stempel)
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Fig. 4: Disc brooch, Junkersdorf, Römisch-Germanisches Museum Köln 51,539 (photo: RGZM/Stempel)
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Fig. 5: Disc brooch, Monsheim, Römisch-Germanisches Zentralmuseum Mainz O.15370 (photo: RGZM/Stempel)
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Fig. 6: Disc brooch, Iversheim, LVR Landesmuseum Bonn 1960.667 (photo: RGZM/Stempel)
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Fig. 7: Disc brooch, St.Severin, Römisch-Germanisches Museum Köln 50.286 (photo: RGZM/Stempel)

N. D. Meeks and R. Holmes described in their article “The Sutton Hoo Garnet Jewellery” an experiment with a scriber that they used to draw the lines directly onto the foils. But in their opinion, the result was not satisfying. (N. D. Meeks/R. Holmes, The Sutton Hoo garnet jewellery: an examination of some gold backing foils and a study of their possible manufacturing techniques. Anglo-Saxon Studies in Archaeology and History 4, 1985, 143-157.) I would like to pick up the idea again, but instead of a scriber I will do the work with a profiled hand-operated tool, comparable to a creaser. It is used until today in bookmaking and leather processing to imprint decorative lines onto a leather surface. In contrast to a pointed scriber the elongated working face of a creaser can be of any cross-section.

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Fig. 8: Creaser (photo: RGZM/Steidl)

 

The theory that has to be verified in practice is as follows:  The grid pattern can be formed with a sliding forward motion of the tool, running it along a ruler with moderate pressure to form parallel lines, then rotating the workpiece by 90 degrees and repeating the action. For my experiments, I will use a small creaser-like tool that I have made by removing the cut of a square rifle file. As foil materials, I will use tin foil (0.03 mm) as well as sterling silver foils of different thicknesses (0,025 mm to 0,04 mm).

Using foil for stone securing

Not a small number of foils seem to have a further purpose: In many cases, the foils are trapped between the stone edges and the surrounding metal of the setting. Is it possible to hold a stone in place with the foil?

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Fig. 9: Disc brooch, Hürth-Kalscheuren, LVR Landesmuseum Bonn XV (photo: RGZM/Stempel)

If times permits, I would like to produce a foil in the way outlined above using a fire-gilded silver foil. In the next few weeks, I will report about my experiments and I am curious about the results and your comments.

 

Featured image: Buckle, Endre socken, Statens Historiska Museet Stockholm 484:12, detail: garnet cloisonné with foils behind the garnets. (photo: RGZM/Stempel)


2 thoughts on “Manufacturing and uses of backing foils – some technical experiments”

  1. Hello Christiane,

    You are lucky to personally check these theories and reconstruct the possible technologies.

    I would be interested if the foils in the adjacent cells have the same irregular grid or only one foil per object shows this pattern. In former case the die and not simply the given foils would have been made by a hand-operated tool.

    It may be of interest to you that there are a few objects from the Hunnic period Carpathian Basin where backing foils were not manufactured by dies but by a hand-operated tool, just as you suggested. The resulted grids are however pretty much more irregular, also their scale is larger than in case of the usual pressed foils.

    Good luck to you with your experiments,
    Eszter Horváth

    1. Hello Eszter,
      Thank you for your comment and I hope it encourages more people to discuss the subject. To answer your question, two of the foils (fig. 3 and 6) are placed in bezel settings and the others are part of a cloisonné setting. In these cases the foils in the adjacent cells have a very similar but not identical pattern. I would be the luckiest person if I found two or more foils with exactly the same irregularities. That would be the evidence that a die had been used! But even while examining a large number of foils, no luck! You mentioned that there are some Hungarian foils that have been made with a hand-operated tool. That’s very interesting. How did you come to these conclusions and what indications support them?
      Christiane

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